Osteosynthesis plates for the treatment of fractures have been known for more than 100 years. The most commonly used osteosynthesis plates have a linear (or elongated) shape and are provided with a plurality of through openings running perpendicular to the plane of the plate. In order to fix an osteosynthesis plate to a bone or bone fragment fastening elements (normally bone screws) are inserted through the through openings into the bone or bone fragment.
For individual cases it has proved convenient to form the through openings inclined relative to the plane of the plate. Often the provision of through openings inclined relative to the plane of the plate is connected with specific anatomical features or with special requirements, such as the generation of compression forces acting at specific angles.
In a linear osteosynthesis plate the alignment of through openings inclined relative to the plane of the plate can in principle be uniquely described by two angles α and β. This situation will now be described with reference to FIGS. 17 and 18.
As illustrated in FIG. 17, a first angle α denotes the inclination of a through opening O with respect to a line S perpendicular to the plane of the plate. The plane of the plate in FIG. 10 is inclined perpendicular to the plane of the drawing. A second angle β denotes according to FIG. 18 an angular alignment of the through opening O within the plane of the plate with respect to a plate longitudinal axis L. The plane of the plate runs in FIG. 18 parallel to the plane of the drawing.
The angles α and β provide an unambiguous angular characterisation by restricting the first angle α to the range from 0° to 90° and having the second angle β run from 0° to 360°. In the following discussion all angles are given in the anticlockwise direction and relative to a directed reference line (for example relative to a plate longitudinal axis pointing in a specific direction).
In U.S. Pat. No. 5,588,674 in FIGS. 5 and 6 a linear osteosynthesis plate is illustrated, which comprises a total of four through openings inclined to the plane of the plate. Each of these four through openings intersects the plane of the plate approximately at an angle of inclination α=45°. The inclined through opening 26b has an angular alignment β=0° with respect to a plate longitudinal axis pointing to the free end 21 of the osteosynthesis plate 20. The remaining three inclined through openings have an opposite angular alignment β=180°.
From DE 199 62 317 A1 a linear osteosynthesis plate is known with two through openings aligned perpendicular to the plane of the plate and two through openings inclined to the plane of the plate. In this osteosynthesis plate the two through openings inclined to the plane of the plate have in each case an angle of inclination α of approximately 65° with respect to a straight line perpendicular to the plane of the plate. The angular alignment within the plane of the plate is in the case of the first inclined through opening β=0° with respect to the plate longitudinal axis, and in the case of the second inclined through opening β=180°.
From Christian Krenkel, Biomechanics and Osteosynthesis of Condylar Neck Fractures of the Mandible, Quintessence Publishing Co., Inc. Carol Stream, Ill., 1994, pp. 56 to 60, further linear osteosynthesis plates are known, which are used to treat fractures of the lower jaw. Since for aesthetic reasons (in order to avoid facial scars) fractures in the region of the lower jaw should be treated by surgical intervention from underneath the jaw, the through openings of the osteosynthesis plates are formed inclined to the plane of the plate. In the proposed osteosynthesis plates the angle of inclination α is between 30° and 90°. The angular alignment β of the through openings is either 0°, 45°, 90° or 135°.
The object of the invention is to provide an osteosynthesis plate for the treatment of fractures, in particular fractures in the region of the head such as lower jaw fractures, which can be fixed in a simple manner and with improved functionality to the bone.